Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

To reconstruct the environmental history including vegetation, fire and climate dynamics, from the Cajanuma valley area (3285 m elevation) in the Podocarpus National Park, southern Ecuador, we address the following major research question: (1) How did the mountain vegetation developed during the late Glacial and Holocene? (2) Did fire played an important control on the vegetation change and was it natural or of anthropogenic origin?. Palaeoenvironmental changes were investigated using multiple proxies such as pollen, spores, charcoal analyses and radiocarbon dating. Pollen data indicated that during the late Glacial and transition to the early Holocene (ca. 16 000–10 500 cal yr BP) herb páramo was the main vegetation type around the study area, while subpáramo and mountain rainforest were scarcely represented. The early and mid-Holocene (ca. 10 500 to 5600 cal yr BP) is marked by high abundance of páramo during the early Holocene followed by a slight expansion of mountain forest during the mid-Holocene. During the mid- to late Holocene (ca. 5600–1200 cal yr BP) there is a significant presence of páramo and subpáramo while Lower Mountain Forest decreased substantially, although, Upper Mountain Forest remained relatively stable during this period. The late Holocene, from ca. 1200 cal yr BP to present, was characterized by páramo; however, mountain forest and subpáramo presented significantly abundance compared to the previous periods. Fires became frequent since the late Holocene. The marked increased local and regional fire intensity during the wetter late Holocene strongly suggests that were of anthropogenic origin. During the late Glacial and early Holocene, the upper forest line was located at low elevations; but shifted slightly upslope to higher elevations during the mid-Holocene.

Abstract:

Late Pleistocene and Holocene vegetation, climate, and fire dynamics, as well as human impact, were studied in the El Cristal region, which is part of the Andean Depression in southeastern Ecuador. The sediment core from a small basin at 2056 m a.s.l. was analyzed by pollen and charcoal analysis and dated by six radiocarbon dates. The record indicates that during the late Pleistocene (ca. 19 750–12 500 cal yr BP) the Upper Mountain Rainforest (UMF), with some smaller areas of páramo and subpáramo were the main vegetation type in the study area. Additionally, there is evidence for Polylepis woodland in the region during this period, which does not exist in the area today. During the transition from the late Pleistocene to the early and mid-Holocene between ca. 12 500 to 3600 cal yr BP, there is a significant presence of mountain rainforest and stable proportions of subpáramo and páramo taxa. The early Holocene from ca. 11 500 to 7800 cal yr BP is characterized by UMF vegetation at the study site. Polylepis became more frequent and reached its maximum. During the mid-Holocene between 7800 to 3600 cal yr BP, the composition of the UMF changed. Polylepis decreased after ca. 4000 cal yr BP, probably due to higher fire frequency. During the mid- to late Holocene, human landscape dis- turbance is evident, especially between ca. 2000 and 1380 cal yr BP, with Asteraceae, Muehlenbeckia/Rumex, Osmunda and Huperzia all increasing in abundance. The late Holocene, from ca. 1380 cal yr BP, was characterized by an increased abundance of páramo taxa and a decrease in mountain rainforest taxa. The expansion of grassland during the late Holocene is interpreted as a result of an increase in human activity, which limited forest vegetation to isolated patches. However, between ca. 1200 and 900 cal yr BP the UMF expanded, probably due to forest recovery after the high frequency of fire. Between ca. 90

Abstract:

Late Holocene human impact and environmental changes were reconstructed from a sediment core of the Laguna Daniel Alvarez (2200 m asl) located on the outskirts of the city of Loja, southeastern Ecuador. Palaeoenvironmental changes were investigated by pollen, spore, algae and charcoal analysis in com- bination with X-Ray Fluorescence (XRF) scanning and element analysis of d13C, Total Organic Carbon (TOC), Total Nitrogen (TN) and radiocarbon dating. This multi-proxy study provides in detail the set- tlement history in the inner-Andean dry valley in southern Ecuador over the last ca. 1400 years. Between 630 and 1470 AD, Zea mays was intensively cultivated around the studied lake by the native Palta culture in the Loja region. After ca. 1470 AD, Z. mays cultivation collapsed, accompanied by an increase in fallow vegetation, such as Mimosa and Poaceae, probably as a result of the Inca invasion and occupation from 1463 to 1531 AD in southern Ecuador. After ca. 1570 AD, Amaranthaceae/Chenopo- diaceae markedly increased, re?ecting the beginning of the Spanish Conquest. In 1531 AD, Loja became Spanish and, during the ?rst ca. 100 years of the Spanish regime, Loja developed into the forti?ed capital of the province. In the 17th century, crop growing strongly declined due to the diminished indigenous population that probably suffered from new diseases introduced by the Spanish invaders. Pinus and Eucalyptus as well as Plantago lanceolata were introduced in the Loja region about 220 years ago.

Abstract:

A lake sediment record from Laguna Campana at 2,488 m a.s.l. in the eastern Ecuadorian Andes allows the reconstruction of local environmental conditions over the past 500 years. A high-resolution multi-proxy approach using pollen, spore, charcoal and XRF analyses provides information about lake genesis, hydrological variations and the development of the surrounding vegetation. Results suggest that Laguna Campana originated from a landslide, which are naturally common and anthropogenically promoted in the study area. Human activities, e.g. deforestation or slash and burn cultivation, impacted the local vegetation development and biodiversity during the recorded period. After a first dense layer of pioneer grasses developed on open soil around the small lake, successional stages of secondary upper mountain rainforest forest mainly composed of Alnus and Weinmannia were observed. The record shows no signs of dense forest regeneration but rather open vegetation with trees and a grassy understory. Especially since ca. A.D. 1980, the proportion of forest in the area was reduced, most probably by fire use for pastures, cultivation and wood extraction. Hydrological variability was derived from differences in minerogenic input and variations in Botryococcus braunii and Sphagnum occurrence. After wettest conditions at the study site, probably triggering the landslide, humid conditions persisted until a time of drier conditions between A.D. 1900 and 1960. A subsequent return to wetter conditions was observed over the last decades. XRF analyses suggest an increase in deposition of atmospherically derived lead since the formation of the lake.